Method for lubricating a rotational-part supporter

ABSTRACT

A rotational-part supporter has a structure in which one of either an inner part or an outer part is fixed, and the other one is rotated, and a main rotational shaft lies between the inner and outer parts. A revolving speed below a revolving speed based on a lubrication lifetime predicted for each rotational bearing ( 3 ) is stored in a memory ( 61 ) disposed in the lubricant supply controller ( 6 ). When a revolving speed obtained by actual rotation coincides with the stored revolving speed in the rotational bearing ( 3 ) after supplying the lubricant, the controller ( 6 ) issues a signal indicating that the lubricant should be newly supplied, and thereby a safety operation can be realized.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a method for supplying the lubricant (i.e., lubricating oil) to a rotational-part supporter that is employed in a rotational device such as an electric motor or a spindle.

[0002] Grease lubrication is a method for applying a fixed quantity of grease onto bearing members when the bearing members are assembled. According to this method, since the machine is operated almost without later grease-resupply, almost all the grease applied when the bearing members were first rotated is scattered to their surroundings, and, as a result, the grease left on the track surface is very small in quantity. Therefore, the bearing members cannot be rotated for a long time, and, in addition, their lifetimes are highly unstable.

[0003] Oil mist lubrication is a method for lubricating a rotational part of a bearing while spraying oil misty onto the rotational part by means of compressed air. According to this method, heat generation can be reduced, and the bearing can be used as a high-speed rotatable one. However, a problem resides in that an exclusive oil mist generator is needed, which raises costs, and in that the emission of exhaust gas that includes oil contaminates the surrounding environment.

[0004] Oil air lubrication is a method for lubricating a rotational part of a bearing with a small quantity of oil by means of compressed air. According to this method, heat generation can be reduced, and the bearing can be used as a high-speed rotatable one. However, a problem resides in that an exclusive oil air-lubricating device is needed, which raises costs, and in that the emission of exhaust gas that includes oil contaminates the surrounding environment.

[0005] Jet lubrication is a method for pouring a large quantity of cooled oil onto a rotational part of a bearing. This method is superior in cooling, and is used for high-speed rotatable bearings. However, disadvantageously, very great power is required to rotate a shaft, and machine costs are high-priced as the machine needs a large quantity of oil that is controlled at a constant temperature. Therefore, this method is applied only to very limited uses, such as bearings of an aircraft engine.

[0006] As described above, all of the conventional methods of lubricating a rotational-part supporter have both merits and demerits. Generally, the quantity of the lubricant to be supplied increases as the speed of the rotational bearing increases.

[0007] However, the prior art according to the aforementioned methods has no basic construction in that the quantity of the lubricant to be supplied is properly varied in accordance with a variation in rotational speed.

[0008] In consideration of the above circumstances of the conventional methods, the present invention aims to provide the basic structure of a lubricating method capable of supplying an appropriate lubricant in accordance with a variation in rotational speed of a rotational bearing.

SUMMARY OF THE INVENTION

[0009] In order to solve the aforementioned problems, the present invention has a rotational-part lubricating method in which, in a rotational-part supporter in which one of either the inner or outer parts is fixed, and the other one is rotated, and a main rotational shaft lies between the inner and outer parts, a predetermined quantity of the lubricant is supplied to a rotational bearing at predetermined time intervals, and either the time interval or a supply of lubricating oil at one time is adjusted or, alternatively, both of them are adjusted in accordance with rotational speed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 shows the lubricant supply device according to a first embodiment, in which (a) is a side sectional view of the direction in which the lubricant is emitted, and (b) is a side sectional view perpendicular to the emitting direction.

[0011]FIG. 2 is a graph for explaining the calculation of proportional distribution in a second embodiment, in which (a) shows the relationship between rotational speed and an appropriate time interval, and (b) shows the relationship between rotational speed and an appropriate supply at one time.

[0012]FIG. 3 is a block diagram for explaining a third embodiment.

[0013]FIG. 4 is a side sectional view showing the structure of a rotational-part supporter to which a method for the present invention is applied, in which (a) shows a case where a rotor is disposed at an inner part, and (b) shows a case where the rotor is disposed at an outer part.

DETAILED DESCRIPTION OF THE INVENTION

[0014] As shown in FIG. 4, the rotational-part supporter that realizes the method for the present invention is formed as a rotational-part supporter (in the case of (a) of FIG. 4) that comprises an outer stator 2 and an inner rotor 1 or as a rotational-part supporter (in the case of (b) of FIG. 4) that comprises an outer rotor land an inner stator 2. In both cases, a rotational bearing 3 lies between the rotor 1 and the stator 2.

[0015] The present invention is characterized in that either of or both of the lubricant supply time with predetermined time intervals and/or the lubricant supply quantity at one time are determined in accordance with the speed of the rotational bearing 3.

[0016] In practice, according to the rotational speed of the rotor 1, a command concerning an appropriate time interval stored in a memory 51 and the lubricant supply quantity at one time is transmitted to the lubricant supply device 4 by means of a computer 5.

[0017] The only way to determine the appropriate time interval and the appropriate supply quantity at one time for lubricating each rotational bearing 3 in accordance with a predetermined rotational speed is to perform trial-and-error experiments. The appropriate time interval and the appropriate supply quantity cannot be calculated at one try by a specific theory.

[0018] Needless to say, the appropriate time interval and the appropriate supply quantity in one time fall within a certain range, and they are not limited to specific values.

[0019] On the other hand, there is a correlation between the time interval with which the lubricant is supplied and the supply quantity at one time. The shorter the time interval, the smaller the supply quantity at one time. The two stand in a roughly proportional relationship.

[0020] If the lubricant supply quantity at one time is too great, the very existence of the lubricant in a rotational bearing causes friction, and raises the temperature of the rotational bearing immediately after the lubricant is supplied.

[0021] Therefore, with respect to each rotational bearing 3, the upper limit of the lubricant supply quantity at one time is based on whether the temperature sharply rises or not immediately after the lubricant is supplied, and the upper limit of such the lubricant supply quantity at one time so as not to bring about a sudden rise in temperature is confirmed beforehand by an experiment.

[0022] By this confirmation, the time just before the temperature is raised can be set as a maximum time interval under a condition where the lubricant is supplied within the upper limit and thereafter the rotational bearing 3 is continuously rotated at a predetermined speed.

[0023] However, a time interval and a supply quantity at one time that can be set with respect to a predetermined rotational speed are not limited to the aforementioned maximum time interval and the upper limit of the supply quantity.

[0024] In other words, it is fully possible to establish an appropriate supply condition in such a way so as to set a standard for a time interval shorter than the maximum time interval and so as to have a supply quantity smaller than the upper limit of the aforementioned supply quantity.

[0025] If the shorter time interval than the maximum time interval is set as a standard, a supply quantity at one time that corresponds to the standardized time interval can be calculated according to the formula: (standardized time interval)÷(maximum time interval)×(upper limit of the aforementioned supply quantity at one time).

[0026] The reason being that there is a roughly proportional relationship between an appropriate time interval and an appropriate supply quantity at one time.

[0027] The supply quantity at one time obtained by the above calculation corresponds to a minimum value of an appropriate supply quantity at one time under the condition of the desired time interval as a result of dividing by the maximum time interval.

[0028] If the lubricant supply quantity at one time is successively increased to be greater than the minimum value under the condition of the standardized time interval, the rotational bearing 3 will be gradually filled with the lubricant, and the temperature of the rotational bearing 3 will gradually rise when the lubricant supply quantity at one time is too great.

[0029] Therefore, the lubricant supply quantity at one time just before a sequential rise in temperature occurs corresponds to a maximum value of an appropriate supply quantity under the standardized time interval.

[0030] Accordingly, if a time interval shorter than the aforementioned maximum time interval is set as a standard, a minimum value obtained according to the above formula, a maximum value confirmed by the above experiment, and an intermediate value between the two correspond to the appropriate lubricant supply quantity at one time.

[0031] Embodiments

[0032] [Embodiment 1]

[0033] Embodiment 1 shows the structure of a preferred lubricating device in the present invention.

[0034] In Embodiment 1, as shown in FIG. 1, a ratchet 42 is rotated by an air cylinder 41 that moves a ratchet pawl 46, and a piston 43 disposed at an end of a screw 47 is slightly moved by the screw 47 disposed at the center of the ratchet 42. As a result, a small quantity of the lubricant is emitted, and thereby the lubricant at one time can be supplied in accordance with a predetermined time interval.

[0035] A gear, instead of the ratchet 42, can be placed and be rotated by a pulse motor.

[0036] If a flow rate control valve 44 is disposed in an operating circuit of the air cylinder 41 as shown in FIG. 1, the supply of the lubricant can be brought into a sluggish state.

[0037] Such a sluggish supply is effective especially when a highly viscous lubricant, such as grease, is used.

[0038] When a highly viscous lubricant like grease is supplied, a necessary quantity of the lubricant cannot be completely emitted by the rapid movement of the piston 43 because of the resistance of the pipe line, but, if air is supplied by the flow rate control valve 44 while taking much time as shown in FIG. 1, the necessary quantity thereof can be completely emitted.

[0039] [Embodiment 2]

[0040] Embodiment 2 is characterized in that the computer 5 calculates an appropriate time interval and an appropriate lubricant supply quantity at one time with respect to the arbitrary revolving speed of each individual rotational bearing 3 in order to automate the lubricant supply method for the present invention.

[0041] This calculation is performed as follows. An appropriate time interval and an appropriate supply quantity at one time are preset with respect to a plurality of revolving speeds. When an input signal by a specific rotational speed (ω) is sent to the computer 5, the rotational bearing 3 selects revolving speeds on both sides that are nearest to the revolving speed according to the input signal, i.e., a maximum value ω₁ of revolving speeds smaller than the revolving speed according to the input signal and a minimum value ω₂ of revolving speeds greater than the revolving speed according to the input signal from among the plurality of stored revolving speeds as shown in the graph of FIG. 2. In order to obtain an appropriate time interval T₀ corresponding to the rotational speed ω₀ according to the input signal and obtain an appropriate supply quantity V₀ at one time, calculation of proportional distribution is performed according to the following formulas as shown in (a) and (b) of FIG. 2:

(T ₁ −T ₀)/(T ₀ −T ₂)=(ω₀−ω₁)/(ω₂−ω₀)

(V ₂ −V ₀)/(V ₀ −V ₁)=(ω₂−ω₀)/(ω₀−ω₁)

[0042] Thereafter, the following formulas are obtained:

T ₀ ={T ₁(ω₂−ω₀)+T ₂(ω₀−ω₁) }/(ω₂−ω₁)

V ₀ ={V ₁(ω₂−ω₀)+V ₂(ω₀−ω₁)}/(ω₂−ω₁)

[0043] where T₁ is an appropriate time interval corresponding to the revolving speed ω₁, V₁ is an appropriate supply quantity at one time, T₂ is an appropriate time interval corresponding to the rotational speed ω₂, and V₂ is an appropriate supply quantity at one time.

[0044] From this proportional-distribution calculation, a known empirical rule exists where, in practice, an appropriate time interval and an appropriate supply quantity at one time can be set with respect to various rotational speeds.

[0045] [Embodiment 3]

[0046] Embodiment 3 is characterized in that, as shown in FIG. 3, a single computer 5 is used for a plurality of rotational-part supporters and a plurality of corresponding rotational bearings 3, thus overcoming the uneconomical situation of Embodiment 2 that employs a system in which a time interval and a supply quantity at one time are determined according to calculations, and in which the computers 5 are assigned to the plurality of rotational bearings 3, respectively.

[0047] However, the computer 5 cannot receive rotational-speed-indicating signals from each of a plurality of rotational bearings and perform calculations simultaneously.

[0048] In Embodiment 3, the single computer 5 is connected to the plurality of rotational bearings 3 through a discrimination circuit 6. Each rotational bearing 3 transmits a rotational-speed-indicating signal and a discrimination signal to the discrimination circuit 6. The discrimination circuit 6 has a circuit part that determines the order of the times when the respective signals have been input.

[0049] If the respective signals are received at different times, a step of temporarily storing the signals in the memory 51 in the order of reception is executed, or, alternatively, the signals are transmitted to the computer 5 without executing this signal-storing step. If apart of or all of the respective signals are received at the same time, the rotational-speed-indicating signals and the discrimination signals that are received at the same time are stored in the memory 51, and the order of the input signals from each of the rotational bearings 3 that are received at the same time is determined according to the order predetermined by a program, and the signals received at the same time are transmitted to the computer 5 in the determined order.

[0050] In order to supply the lubricant on the basis of the signals that indicate the speed of each rotational bearing 3 that is sequentially transmitted by the discrimination circuit 6, the computer 5 can perform calculation of an appropriate time interval and an appropriate lubricant supply quantity at one time, and can transmit output signals resulting from the calculation to each rotational bearing 3 on the basis of the discrimination signals sent from the discrimination circuit 6.

[0051] As described above, in Embodiment 3, the rotational-speed-indicating signals and the discrimination signals are sequentially input from the discrimination circuit 6 to the computer 5 according to a predetermined order, and a given calculation is performed even if the rotational-speed-indicating signals are input from the rotational bearings 3 at the same time. Therefore, serious obstacles do not arise in controlling an appropriate time interval and an appropriate supply quantity at one time.

[0052] Effect of the Invention

[0053] In the present invention having the above-mentioned structure, the lubricant can be supplied rationally and appropriately, and thus an accident due to the wear of a rotational bearing can be prevented, and the rotational bearing can be safely operated for a long time.

[0054] Especially in the device of Embodiment 1, the present invention can be suitably applied to the lubricant supply, and appropriate processing can be applied to a highly viscous lubricant such as grease.

[0055] According to the computer processing of Embodiment 2, automatic control can be carried out for an appropriate time interval and an appropriate supply quantity with respect to various rotational speeds. According to the system of Embodiment 3, a single computer can operate a plurality of rotational bearings extremely economically.

[0056] Thus, the present invention has multifaceted merits, and its value is great. 

What is claimed is:
 1. A method for lubricating a rotational-part supporter, the rotational-part supporter having a structure in which one of either an inner part or an outer part is fixed, and the other one is rotated, and a main rotational shaft lies between the inner and outer parts, the method comprising a step for supplying a predetermined quantity of the lubricant to a rotational bearing at predetermined time intervals and a step of adjusting either of or both of the time interval and/or the lubricant supply quantity at one time in accordance with a rotational speed.
 2. The method for claim 1, further comprising: a step of confirming an upper limit of such the lubricant supply quantity at one time so as not to allow a temperature of the rotational bearing to sharply rise by experiments on the basis of whether the temperature of the rotational bearing sharply rises or not immediately after the lubricant is supplied; a step of supposing that a time quantity until just before a temperature-rise occurs is a maximum time interval in a case where the rotational bearing is continuously rotated at a predetermined rotational speed while receiving the lubricant supply quantity of the upper limit at one time; and a step of setting a time interval shorter than the maximum time interval as a standard time interval and determining a minimum value of the lubricant supply quantity at one time corresponding to the standard time interval such that the set time interval, which has been set as a target, is divided by the maximum time interval and is multiplied by the upper limit of the lubricant supply quantity at one time.
 3. The method for claim 1, further comprising: a step of confirming an upper limit of such the lubricant supply quantity at one time so as not to allow a temperature of the rotational bearing to sharply rise by experiments on the basis of whether the temperature of the rotational bearing sharply rises or not immediately after the lubricant is supplied; a step of supposing that a time quantity until just before a temperature-rise occurs is a maximum time interval in a case where the rotational bearing is continuously rotated at a predetermined rotational speed while receiving the lubricant supply quantity of the upper limit at one time; and a step of setting a time interval shorter than the maximum time interval as a standard time interval and determining a maximum value of the lubricant supply quantity at one time corresponding to the standard time interval on the basis of the lubricant supply quantity just before a temperature-rise sequentially occurs when the lubricant is supplied at the time intervals.
 4. The method for claim 1, further comprising a step of selecting a time interval as a target and thereafter selecting an intermediate value between the minimum value of the lubricant supply quantity at one time as recited in claim 2 and the maximum value of the lubricant supply quantity at one time as recited in claim
 3. 5. The method for claim 1, further comprising a step of providing the lubricant emitting device in which a revolving screw is rotated by a gear that is rotated by a ratchet or a pulse motor that rotates on the basis of an air cylinder, and a piston at the tip of the revolving screw is moved.
 6. The method for claim 5, further comprising a step of providing the air cylinder that rotates the ratchet with a flow rate control valve in a path through which a pump is supplied so as to adjust the lubricant supply speed.
 7. The method for claim 1, further comprising: a step of prestoring both the lubricant supply time interval and the lubricant supply quantity at one time that correspond to a plurality of rotational speeds in accordance with a revolving speed of each rotational bearing; a step of standardizing a corresponding time interval and a corresponding supply quantity at one time in a minimum value of a rotational speed larger than the rotational speed by the input signal and a maximum value of a rotational speed smaller than the rotational speed by the input signal of a plurarity of rotational speeds prestored with respect to an input signal by an actual rotational speed maintained in the rotational bearing; a step of performing a proportional-distribution calculation based on a difference with the rotational speed by the input signal; a step of calculating an appropriate lubricant supply time interval and an appropriate lubricant supply quantity at one time that correspond to the rotational speed by the input signal; and a step of issuing a command to the lubricant supply device.
 8. The method for claim 1, further comprising: disposing a single computer connected to a plurality of rotational bearings through a discrimination circuit, each rotational bearing sending a rotational-speed-indicating signal and a discrimination signal to the discrimination circuit, the discrimination circuit including a circuit part that judges of order at which the signals are input; in a case where the respective signals are received at different times, executing a process of temporarily storing each of the signals in a memory or, alternatively, sending the signals to the computer without executing the signal storing process according to the order of reception; in a case where a part of or all of the signals are received at the same time, storing the rotational-speed-indicating signal and the discrimination signal that have been received at the same time in the memory, and determining the order of the input signals from each rotational bearing that are received at the same time according to the order predetermined by a program; sending each of the signals received at the same time to the computer according to the later determined order; allowing the computer to perform calculations of an appropriate time interval and an appropriate lubricant supply quantity at one time in order to supply the lubricant on the basis of the signal that indicates the speed of each rotational bearing that is sent from the discrimination circuit; and sending an output signal based on the calculation to each rotational bearing on the basis of the discrimination signal sent from the discrimination circuit. 